1. Field of the Invention
The present invention relates generally to a programming technology for a robot and, more particularly, to an offline teaching apparatus for teaching, in an offline mode, a processing work of a robot.
2. Description of the Related Art
In a manufacturing system using a robot, especially an industrial robot, a processing robot system in which processing work, such as arc welding, is performed on a workpiece (i.e., an object to be worked) by a processing tool (i.e., an end-effector) attached to the end of a robot arm, has been conventionally known. In this type of robot processing system, in order to improve working efficiency in a manufacturing site, an offline teaching procedure, in which a processing work is taught without performing the operation of an actual robot, is employed. In the offline teaching procedure, the models of the robot and its working environment are provided in a computer, and the robot model is manipulated, on a display screen, to simulate a desired robot operation, so that position/orientation data, motion sequence data and process condition data, which are to be taught to the actual robot, are thus obtained.
Usually, when an offline teaching procedure is implemented in the processing robot system, an offline teaching apparatus, constructed by installing required software on a computer, prepares a processing program by using the models of a robot and its working environment, and thereafter passes the processing program to a robot controller controlling an actual robot, so as to cause the robot to perform, as a trial, the processing work on a workpiece under the control of the robot controller. Then, while checking the quality of the processing work, an optimal processing program is determined, by adjusting an arm orientation for a processing, a processing sequence for taught points, processing conditions, etc., and/or by adding commands to meet requirements. In this connection, processing conditions generally include conditions relating to the motion a robot arm, such as speed, acceleration, interpolation mode, etc., as well as conditions relating to the details of the processing work, such as welding current, laser power, etc.
In the manufacturing site employing the above-described processing robot system, there is a case where similar processing works are performed on workpieces having mutually similar geometrical features, such as shapes, dimensions, etc. In this case, if various data included in a processing program that has been prepared for a specified workpiece can be also used in another processing program to be prepared for another workpiece having similar geometry (i.e., a similar workpiece), it is expected that a programming procedure for a robot in relation to the similar workpiece can be facilitated, which may contribute to a further improvement of working efficiency in a manufacturing site.
For example, Japanese Unexamined Patent Publication (Kokai) No. 6-337711 (JP-A-6-337711) discloses an offline teaching apparatus, for a welding robot, in which teaching data (or a master program) for a workpiece having a basic shape (i.e., a basic workpiece) is used to prepare teaching data for a similar workpiece that can be constructed by the size-enlargement, the size-reduction and/or the parts-combination of the basic workpiece. The teaching data for the similar workpiece include position data prepared by modifying position data in the master program through the size-enlargement, the size-reduction and/or the parts-combination, as well as orientation data and welding condition data, which are the same as orientation data and welding condition data in the master program.
Also, Japanese Unexamined Patent Publication (Kokai) No. 2004-362018 (JP-A-2004-362018) discloses an offline teaching procedure, in which orientation data at respective taught points in existing teaching data relating to a specified workpiece is converted to orientation data at corresponding taught points relating to a similar workpiece, and thereby preparing teaching data for the similar workpiece. In this procedure, positions of the respective taught points for the similar workpiece have been set in advance.
In the conventional offline teaching apparatus as disclosed in JP-A-6-337711, it is possible to accomplish programming, based on the master program, only for a similar workpiece that can be constructed by the size-enlargement, the size-reduction and/or the parts-combination of the basic workpiece. In other words, it is not possible to accomplish programming, based on the master program, for a workpiece having such a shape as to require modifying the orientation of a robot in a welding work for the basic workpiece.
On the other hand, in the offline teaching procedure disclosed in JP-A-2004-362018, only the orientation data are used, from among the existing teaching data, for a programming procedure for a similar workpiece, and it is thus presupposed that the positions of the respective taught points for the similar workpiece are also be set in advance. The previous setting of the positions of the taught points requires profound knowledge and skill regarding the processing work.